Christian bakers sued for refusing to make a cake with a pro-gay marriage slogan face being forced to express a political opinion in conflict with their faith, Northern Ireland's top law officer has argued.

Christian bakers sued for refusing to make a cake with a pro-gay marriage slogan face being forced to express a political opinion in conflict with their faith, Northern Ireland's top law officer has argued.

Attorney General John Larkin QC told senior judges the McArthur family should have constitutional protection for turning down a customer's order based on their religious beliefs.

Mr Larkin has intervened to back the owners of Ashers' bakery in their bid to overturn a ruling that they acted unlawfully.

Last year Belfast County Court held that the firm discriminated against Gareth Lee on grounds of sexual orientation and religious belief or political opinion.

In a landmark case, the Co Antrim-based company was ordered to pay the gay rights activist £500 in damages.

Mr Lee had requested a cake depicting Sesame Street characters Bert and Ernie below the motto 'Support Gay Marriage' for an event to mark International Day Against Homophobia.

Bosses at the bakery, run by the McArthurs, refunded his money for the order placed at its Belfast city centre shop in May 2014 because the message went against their Christian faith.

Although the family insist their problem was with the cake and not the customer, Mr Lee claimed he was left feeling like a lesser person. In a case he brought with backing from the Equality Commission, the County Court held that business was not above the law.

Ashers is challenging the verdict, with its legal team insisting it was wrong to force it to choose between operating a business or adhering to its faith.

The Court of Appeal was told the family believed it would have been sinful to bake a cake with the gay marriage message.

Mr Larkin has now stepped in to examine sexual orientations regulations at the centre of proceedings, and whether they directly discriminate against those who hold religious beliefs or political opinions.

On day two of the appeal hearing he said: "There are very large questions about the role of conscience in all sorts of business."

A panel of three judges led by Lord Chief Justice Sir Declan Morgan were told the dispute centred on expression.

"I say very clearly, if it was a case where Mr Lee had been refused some of Ashers' excellent chocolate eclairs because he way gay or perceived to be gay, I would be standing on the other side of the court," the Attorney General said. "But it's not about that, it's about expression and whether it's lawful under Northern Ireland constitutional law for Ashers to be forced... to articulate or express or say a political message which is at variance with their political views and in particular their religious views."

In written arguments which formed part of his case, he questioned whether the Fair Employment and Treatment (NI) Order 1998 would compel Ashers to put the words 'There is no God' or 'Christianity is a lie' on a cake.

According to the Attorney General, the right to decline to express a view inconsistent with religious belief is protected under the European Convention on Human Rights (ECHR).

Robin Allen QC, for Mr Lee, noted the cake order was refused 10 days after the Assembly had again voted against introducing same-sex marriage.

He told the court the case was indisputably about political opinion. The barrister contended: "The single core point which divides an act which would be favourable to an individual from the act which occurred - it's one word, the word 'gay'.

"Take that out (and leave) 'Support marriage' or 'Support Christianity' or 'Support opposite sex marriage'... all of those things would have led to a different course of conduct."